Leaf teeth

…why, and why not, do leaves have them?

How often it happens—you can walk past something for years and never think twice about it or even notice it at all. Then, once it is called to your attention, you begin to see that something rather often.

Cottonwood (top) and alder (bottom)

That happened to me (again) quite recently. I read an article about the teeth that are found around the edges of certain kinds of leaves. For instance, alder leaves always have noticeable teeth, and even cottonwoods have small teeth that are evident upon close inspection. Of course, for years, I had known about teeth on the margins of alder leaves, but had I thought about them??? Hmmmmm—-no. So now is the time.

Researchers have known for a century that toothy leaves seem to be more common on modern species of trees and shrubs that live in cooler climates, and that association has long been used to reconstruct ancient climates from collections of fossilized leaves. For example, fossil leaves in south-central Alaska were used to support other information showing that Alaska had a much warmer climate millions of years ago. Recent studies, however, suggest that the correlation between toothiness and cool climate is not quite as simple as was commonly supposed, so the modern correlations of the distribution of leaf teeth with climate may not be as precise an indication of past climates as previously thought.

There remains a significant correlation of the occurrence of toothy leaves with cooler climates, however. So then it becomes interesting to consider what leaf teeth do for the plants that bear them.

It turns out that leaf teeth can enhance the rates of carbon uptake early in the growing season. This is particularly important for plants that grow in regions where the growing season is short (i.e., cooler climates). In general, the margins of leaves have high physiological activity early in the season, and toothed margins accomplish more photosynthesis and water transport than untoothed margins. Furthermore, species in the northern U.S. tend to do these things better than southern ones.

Thus, in cool, short-season climates, where rapid early-season growth is especially useful to the plant, leaf teeth are advantageous. A possible disadvantage is increased water loss (all that physiological activity uses water). And so it is presumably no accident that the correlation of leaf teeth with cooler annual temperatures is found where water is not in limited supply; in dry regions, any gain in photosynthesis and energy for growth is outweighed by the problem of water loss.

That’s all well and good, but as usual, it leaves us (me, anyhow) with more questions. For instance, consider our many species of Alaskan willow: some species have toothy leaves and others don’t. (Blueberry species also differ in this way.) Do those with leaf teeth tend to send out leaves earlier in the season, because they can function better than the rest when temperatures are cooler? And even within a single species of willow, some individuals are toothier than others. Do these individuals live in cooler spots or do they only make leaf teeth in cooler years? Then there is the observation that even on a single plant, there is variation in the development of leaf teeth. Are the toothy leaves the first to appear each season, when the weather is cool? And does it matter how big the leaf teeth are? Cottonwood leaf teeth are much smaller than those on alder leaves…

This story is still unfolding, so there is, at present, no last word on the subject. That’s one of the interesting things about science: every idea is continually subject to possible revision as more information comes in.


June treasures

a flower show, a rare bird, and an elusive insect

June always brings lots of small nuggets of natural history to our attention—it might be a junco nest next to a busy trail but sheltered deep in a cubbyhole under an overhanging tuft of long grass, or a patch of devil’s club stems well off any human trail but with every single bud neatly removed, or terns bringing fish to their voracious chicks, or a bear, far up in a cottonwood, breaking branches to eat the maturing pods.

Here are three vignettes that I found very satisfying:

–A stroll through the meadows along Cowee Creek yielded a spectacular flower show. In mid to late June, shades of purple ruled the fields: wild iris, northern geranium, beach pea, and lupine, with touches of pink roses, yellow buttercups, and white cow parsnip. We noted more than forty species of flowers in just a few hours, without even trying to identify the sedges and grasses. A little later on, these meadows will be dominated by pink fireweed and more white cow parsnip.

–A walk in the Gustavus area surprised us with frequent sightings of twayblade orchids of two distinct species. Their tiny flowers must be pollinated by miniscule flies or something similar. Best of all was the finding of a black-backed woodpecker nest in a dead spruce. We heard two kinds of unrecognized calls coming from somewhere not far from the trail. Seeking their source, we discovered that a continuous shrill call came from a hole about six feet above our heads; a nestling or two were calling to parents for food, more food. The other call, however, was coming from a fledgling woodpecker with a yellow patch on its head and black back. Still rather frowsty and disheveled, somewhat clumsy when landing, it repeatedly announced its displeasure at our intrusion. No parents came near while we were there, and may have been away for a while, judging from the endless shrilling of the chick(s) still in the nest. Finding this nest was a minor coup, because this species is not seen very often around here.

Photo by Bob Armstrong

–Another day found three friends partway up Fish Creek, in search of a mysterious little aquatic insect called the mountain midge. They are true flies but a very primitive sort. Only six species are known from North America. We’d tried to find them once before, but now was the right season. Rubbing the rocks in a stretch of fast water dislodged larval mayflies and some caddisflies and, finally, some larval mountain midges.

These larvae were very small, perhaps three to five millimeters long (there are roughly 25 millimeters to an inch), with three stubby prolegs on each side. Each proleg has a tiny suction cup ringed with miniscule hooks. The larvae creep over the rocks, holding on tightly, eating the algae and bacteria that coat the rocks.

Hatching from eggs that overwintered in cold, fast water, the larvae eat and grow for several months and then mature into tiny flying midges. The adults have no functional mouthparts, so they cannot feed, and they only live for an hour or two. That’s a pretty short time in which to find a mate and lay the eggs of the next generation. And I have to wonder just how they manage to colonize new habitats that open up, for example, when glaciers retreat. But they must have done so frequently in the course of history.

Hunting success

… you can’t win ’em all

One day this fall I watched a juvenile great blue heron that was fishing in Steep Creek. In typical heron fashion, it stood motionless for long minutes, then quickly jabbed its long bill down into the water after some hapless little fish that passed by. When one hunting spot petered out, the bird moved over to a new perch and waited again. Altogether, it made over a dozen tries to capture a fish and succeeded about one third of the time. A success rate of about thirty-three percent is not too bad, although an adult, with more experience, would likely have done better.

Those observations got me thinking about the success of predators in general. How often are they successful in prey capture? What proportion of capture attempts is successful?

Perhaps the best-studied wild predator in North America is the wolf, so that is a good starting place. Admired for their strength and intelligence, respected for their close family life, wolves are sometimes reviled as competitors to human hunters. Just how successful are wolves, when they go hunting? I focused on wolves hunting ungulates (such as moose, deer, sheep), because that interaction has been the most studied. Wolves also eat beavers, hares, mice, and fish, of course, but there are no data available on those interactions.

Hunting success of wolves obviously varies with many factors, including prey density, wolf pack size, physical condition of the prey, snow depth, escape routes for prey, and so on. Reviewing a number of research reports, I found that, for wolves hunting moose in winter, as many as 38% of hunts might be successful, but usually fewer than 10% of hunts are successful. And captured prey is sometimes lost to scavenging ravens or bears.

It is interesting to compare those figures with those (courtesy of ADFG) for human hunters of moose. The average recorded success rate over a ten-year period for much of Southeast was less than 25% (with the notable exception of one subunit in which humans were successful 63-100% of their hunts!). To take two examples from farther north: In Kenai and Talkeetna, 10-22% of moose-hunters were successful.

It is harder the find data on the frequency of moose kills by wolves, which also varies enormously. Although wolves are capable of killing two moose in one day when hunting is easy, far more commonly there are three or four days between kills (sometimes even eleven days or more). Records for human hunters show that it often takes two to four days for a successful hunter to get a moose.

Although statistical comparisons are not feasible, the data suggest to me that human hunters often have higher success rates than wolves, when hunting moose. In addition, there are at least three salient differences between wolves and humans as predators of moose. Wolves are not constrained by regulations; in the absence of regulation, the human success rate would probably be still higher. Each human hunter generally takes only one moose per season, but of course the wolves hunt repeatedly throughout the year. Hunts by humans tend to be heavily concentrated in areas that are easy of access (around settlements, or a short boat ride from town, for example), sometimes to the point that the prey population is quite depleted in those areas. In contrast, wolf hunts are typically widely spaced, often many miles apart, as each wolf pack ranges over its large territory.

Wolves hunting deer in winter are recorded to be successful on fewer than 20% of their hunts, although occasionally they may succeed up to 50% of the time. By comparison, humans in Southeast were successful 30-71% of their hunts (in various management units), on average. For Dall sheep, wolves caught one in fewer than 33% of their hunts, and humans averaged 28-46% success. Again, the numbers suggest that humans often may be somewhat more successful than wolves.

Bald eagles are another fairly well-studied wild predator, and data are available from all over North America. There are a few reports that eagles are more successful in capturing fish than waterfowl (for instance, 90% vs 20%, respectively), but most reports do not separate the two sorts of prey or the age of the eagles. Nevertheless, when fish comprise at least 90% of prey taken, the success rates tend to be quite high, ranging from 47% to 73%. In these cases, there was no information on what species of fish were caught, and I found no data on eagles catching salmon or herring, which would be very relevant here in Southeast.

For fun: here are a few other serendipitous bits of data: Coyotes hunting snowshoe hare succeeded 28-69% of the time, compared to 20-40% for lynx hunting hare in the same area. Orcas hunting minke whales off the shores of British Columbia and Southeast Alaska were successful in four of nine observed hunts (45%); orcas hunting humpback whales in Argentina were successful 21% of the time in open water and 34% of attacks on beached whales. Great blue herons in Nova Scotia were successful in 29-100% of their strikes on fish prey.

One striking feature of such observations is that hunting success for any species varies enormously, which must have huge consequences for the predators. I did not find information on how much energy is expended on a hunt (and perhaps how much energy is spent defending the catch from competitors) compared to how much each predator gains by eating the captured prey. Some times or places might make it easy to obtain the energy needed for daily maintenance and for reproduction. But many predators must sometimes be close to starvation, and thus be faced with the hard choice of whether to hunt harder or to rest in order to conserve energy. The critical importance of getting enough food is one reason that juvenile animals commonly have a high mortality rate, before they learn to become proficient hunters. Some predators, including orcas and wolves, often use sophisticated strategies and complex tactics in capturing prey, and in such cases, the learning period for juveniles is extended to several years.

Highbush cranberry

a worthy berry…and a mysterious fungus

Autumn in Juneau can be a bit difficult—shortening days, lots of rain (in my neighborhood, there has been much more than the official numbers!—flowers on my deck actually got moldy), migrating songbirds flocking up and leaving us for the south, the end of the flowering season. But there is always (at least) one outdoor thing I look forward to—the ripening of highbush cranberries. And this year there was a bumper crop.

One thing should be made clear here at the beginning: high bush cranberries are not cranberries and they are not even related to true, bog cranberries. Bog cranberries (and domestic cranberries) are related to blueberries; they thrive in muskegs, their frail little vine-like stems crawl over the moss, and the seeds are tiny. The so-called highbush cranberries grow on whippy shrubs up to ten or more feet tall, have big, flat seeds, and are related to honeysuckles and elderberry. What the two kinds of ‘cranberries’ have in common is a tart flavor and a brilliant red color when ripe.

Bog cranberries are good-tasting and useful for making a holiday drink or sauce for turkey, but it’s a lot of stoop-labor to harvest them. I like the highbush cranberries for several reasons: the shrubs are decorative much of the year, from the showy clusters of white flowers in early summer to the scarlet leaves and berries in fall. Harvesting them is much easier—no stooping. The berries are reported to have high levels of vitamin C and antioxidants. And, although they too can be made into holiday drinks and jelly, even better, to my taste, is the pungent, savory ketchup that some of us like to make (and especially eat!). The ketchup is good on fish and other meats, potatoes, cheese sandwiches, and no doubt other things still to be tried.

The university extension service website has a list of publications, and one of these features highbush cranberries. Look for the article by Dinstel and Johnson in 2011, labeled as FNH-00112. You’ll find some good recipes there.

We are not the only ones who like highbush cranberries. We see evidence on the trails that bears have eaten good numbers of them, but, oddly, many of the berries pass through their digestive tract whole. Birds can eat them, but smaller birds would spit out the big seed. Being eaten by a vertebrate is how the seeds are moved around the landscape; the lucky ones germinate and grow into new shrubs. In some areas of Alaska, the twigs are sometimes an important source of browse for moose, too.

One day last year I walked the Herbert River trail with a friend, and we noticed something new to us. Some of the highbush cranberry bushes along the trail had strange, rough-surfaced, dark, lumpy cankers on the stem. One of the Forest Service forest pathologists at the Juneau Forestry Sciences Lab very kindly followed up on this observation, sending the specimens to a genetics lab for identification. It turns out to be a rust fungus (Puccinia linkii) that is also reported from highbush cranberry shrubs in western Canada and elsewhere. This rust can overwinter in infected stems or on infected leaves that have dropped to the forest floor, sending out spores that start new infections on leaves, flowers, stems, and berries in spring. Spores are can be produced on any of these infected plant parts, facilitating further disease spread throughout the growing season; some leaves become conspicuously dotted with numerous spore-bearing bodies. Spores spread when blown about by the wind or rain-splash. Interestingly, the common stem infections in the Juneau area are apparently rare or undocumented elsewhere, as this fungus normally only or primarily affects the foliage .

Photo by Robin Mulvey

Research in British Columbia has shown than this rust infection can affect the shrub in several ways. Berry production is reduced, and the berries that do develop contain less sugar than normal. Heavily infected leaves die off early, so the plant loses some ability to synthesize carbohydrates, and infected twigs are likely to die an early death too.

The FSL forest pathologist, Robin Mulvey, has so far mapped the occurrence of this fungus at several spots in the Juneau area from the Valley to Out the Road, but not south of the Valley. She is interested to learn of other sites with infected highbush cranberry shrubs. If you see signs of this rust fungus on highbush cranberries in Juneau or elsewhere in Southeast, please notify her at rlmulvey@fs.fed.us or 586-7971.

Fossil hunting in Juneau

just look for the Gastineau Formation

My two companions scrambled up the soggy slope with agile ease, and I lumbered along behind. My main job, as usual, was to throw sticks for the four-footed friend, but our real mission was finding fossils. Around Juneau, we don’t expect to find dinosaurs, ichthyosaurs, or mammoths, such as those found up north. Nor do we find fossil remains of bears, caribou, and foxes, such as those in Prince of Wales caves. Nope, nothing quite so spectacular.

However, we can find lots of invertebrate fossils: shells of clams, snails, barnacles, cases of certain polychaete worms, bits of sea urchin shells, and—for the really persistent, dedicated, and knowledgeable searchers—microfossils, identifiable only under a microscope, including a great diversity of foraminifera. “Forams” are amoeboid protozoans that make sometimes elaborate shells, usually of calcium carbonate. Some live as plankton but they are reportedly more often associated with sediments.

On this day, our search for shells was almost immediately successful. A tiny rivulet ran down the forested slope and we followed its course upstream. Eventually we came to an even smaller side drainage that was little more than a seep. Along the sides of the seeping area, near the confluence with the rivulet, the mud had sagged and slumped, and there—poking up out of the gooey mess—was an intact snail shell. Whoopee! Picking through the muck yielded several broken clam shells too, and we felt amply rewarded for our small efforts.

These shelly fossils are found in what’s known as the Gastineau Formation, named (of course) for our local channel, where it is commonly observed (although similar formations are known farther south). The formation is typically composed of variable proportions of fine silt, sand, gravel, and sometimes cobbles, deposited on and along marine beaches during and after the last principal glaciation. Some glacial material was added as it washed down from the big ice or was carried around by bergs. The known ages of the deposits range in the vicinity of ten to twelve thousands years ago.

As sea levels rose (relative to the land, which also began to rise) when the big ice retreated, beaches were formed and inhabited by a great diversity of invertebrates; as sea levels fell (again relative to the rising land), the beaches were abandoned by the sea and many of their inhabitants were stranded and died, leaving their hard parts in the sediments. One list of the diversity of animals found in the Gastineau Formation includes at least twenty kinds of clams, about eighteen kinds of snails, and dozens of kinds of forams, plus a variety of other creatures.

Clam shell from the Gastineau Formation. Photo by Katherine Hocker

The Gastineau Formation is exposed at numerous locations in Juneau: along road cuts, stream cutbanks, slumping slopes, construction sites. It occurs at three levels, up to about 750 feet above present sea level, showing that beach formation and abandonment happened several times. The layers of the formation vary in thickness, from just a few feet to several tens of feet in depth. Composition and density of the sediments differ among the levels and among locations where the formation is exposed. Of course, the composition of the invertebrate fossil fauna varies too, and researchers can tell, by the nature of the sediments and by the relative abundance of different species of fossil, what the conditions were like on these abandoned beaches—if this was a place of quiet water or turbulent waves, of brackish or salt water, of very shallow or somewhat deeper water, and so on.

For most of us, the invertebrate fossils are not as exciting as the big stuff. But they are interesting and instructive all the same, providing insight into changes in our so-changeable landscape.

Thanks to a friendly local geologist for useful references.

Crossbills nesting in winter

…here we go gathering twigs and moss…

Once again, this time in late February, the Auke Nu trail was in top shape, firm snow all the way to the cabin. As we sashayed along, I heard some soft and gentle warbling notes high in the canopy. I finally spotted some movement under a clump of moss that seemed to be growing on top of a witch’s broom (a parasite that distorts branch growth).

Underneath that clump of moss were three female red crossbills, busily selecting short twigs. They seemed to be the source of the songs I heard, although female crossbills don’t sing as much as males do. There is no indication in the literature that females sing a little song when gathering nest material. (But I’m tempted to suggest “Here we go gathering twigs and moss, twigs and moss, twigs and moss…”) I suppose it’s possible that some males were hanging around in the dense hemlock foliage nearby and providing the sound effects.

Crossbills often nest in loose clusters, several nests fairly close together. Females build the nests, although males may sometimes carry nest material. They can nest at virtually any time of year, even in the dead of winter. Nesting is initiated when females have enough food to develop eggs and can see that there’s lots of food still around for raising chicks. So when there is a big cone crop, as there is this year, they gear up for making babies.

Crossbills are nomadic, moving around from region to region, in search of good cone crops. If they find a really good one, they may stay and rear two or three or even four broods in one place. If not, they move on and rear a series of broods in different areas. Breeding is so tightly linked to food supply that young females only six months old can sometimes breed in a good cone year.

Even when the cone crop is good, things can still go awry. Crossbills are specialized to pry open cones and extract the seeds. They are most efficient at foraging from conifer cones and less efficient at eating other kinds of seeds. But if the air is dry for a period of time spruce and hemlock cones may open spontaneously and release the seeds to fly away on the wind. Dispersal of the seeds clearly reduces the availability of seed-laden cones for crossbills, but it allows the seeds a chance to escape seed predation by these birds and perhaps produce some seedlings.

As we walked along the trail, we noticed very localized patches where the ground was covered with tiny hemlock twigs and empty cones. We surmised that these patches were under trees where crossbills had been foraging. Crossbills often tear a cone off the branch, hold it in one foot, and pry out the seeds, letting the empty cone drop.

In addition to several groups of red crossbills, I heard what sounded like swarms of white-winged crossbills as we went up the hill (although one of Juneau’s ace birders says that one white-wing can sound like a whole bunch…). White-wings are probably nesting now too. Like the red crossbill, they are nomadic, can nest at any season if there’s a good cone crop, and often nest in clusters. Their breeding range goes as far north as the treeline but overlaps that of the red crossbill all across southern Canada and into the Rockies of the northern U.S.

White-winged crossbills male (L) and female (R). Photo by Bob Armstrong

Both species irrupt southward when cone crops fail in the north. Young crossbills and females are subordinate to older birds and males and are the first to feel the pinch of hunger. They often move well ahead of the dominants, leaving an area earlier and sometimes going farther south, almost to the Gulf coast. They seldom breed in the southern regions, however, and move north again in search of good cone crops.

Looking at intertidal algae

a neophyte’s view

The tide was moderately low, a minus 3.9 or so, and four of us had the privilege of tagging along with a genial visiting algologist (technically a phycologist) on a stroll through the intertidal zone. As true neophytes (the word literally means ‘new plant’!), we hoped to learn to identify a few of the common intertidal algae. Knowing the name of an organism is just a beginning: if you know the name, then you can probably look it up and find out a bit more about its natural history. A name in a vacuum isn’t very interesting!

We ambled across rocks and mudflats as the Latin scientific names (along with identification cues) were dropping thick and fast. One of us took notes, rendering the names phonetically—to be corrected later, along with brief tidbits of natural history—to be amplified later. So we had home work to do (as did the algologist, whose specimen bag was getting fat).

There are thousands of species of algae, ranging in size from microscopic one-celled kinds to giant meters-long kelps, and ranging in form from strings and ropes, to bristly mats and dainty frills, to hefty blades, to bubbles and blobs, and everything in between. Their life histories are equally varied, spurring me to contemplate a future essay on what is called ‘alternation of generations’, something that is characteristic of many plants but not found in animals.

In the meantime, here is a tiny sample of our finds on this excursion—the ones we found most readily distinctive.

–Sea cauliflower (a.k.a. sea potato or brain seaweed). Leathesia marina, classified as a brown alga. This is a lumpy, spongy, yellowish-brown alga, hollow except when quite young; when this blob is squeezed, it breaks apart into filaments, not mush. It is an annual plant (meaning that it does not live from year to year) in the mid to low intertidal zone. It often grows as an epiphyte on other species of algae, but it also grows on rock. The visible blob produces spores that germinate into tiny egg- and sperm-producing plants; when a sperm fertilizes an egg, the resulting zygote grows into the spore-producing blob. The alternation of a spore-producing plant with a gamete-producing plant in the life cycle is the basis for the term ‘alternation of generations.’ One research study found that mortality increased when the plants were crowded and when wave action became too severe. This is one of several species of alga that have antiviral properties and therefore some medicinal value for humans.

Studded sea balloons. Photo by Kerry Howard

–studded sea balloons. Soranthera ulvoidea, classified as a brown alga. The ‘balloons’ are pale brownish sacs up to about two inches long. The surface is studded with darker pimples, which indicate locations of spore formation. As in the sea cauliflower, the spore-producing individual grows from a fertilized egg on a small plant in the alternate portion of the life cycle. This species is an annual that only grows as an epiphyte on other algae of two particular genera. A researcher investigated the possible consequences of this epiphyte on the host, and found that the presence of the epiphyte increased the drag (caused by water currents) on the host and tended to make the host detach from its substrate (which is generally lethal to the host), but sometimes the epiphyte detached first, and no harm came to the host. Indeed, it seems that the presence of the epiphyte reduced grazing on the host by amphipods, which preferred to eat the epiphyte.

Sea sacs

–sea sacs (Halosaccion glandiformis), classified as a red alga. The long, slender, thin-walled, finger-like sacs are reddish-purple when young but bleach to brownish-yellow as they age during the summer, before dying back in the fall. Each sac is perforated with tiny pores that let in sea water. The sacs fill with water except for a gas bubble at the tip. When exposed to air, the sacs lose water by evaporation and through the pores, while surface tension at the pores prevents entry of air. A good supply of internal water allows the sacs to survive exposure to air longer than if the sacs are empty; photosynthesis (the process by which carbon dioxide and water are converted to carbohydrates and oxygen) can be conducted using carbon dioxide from the contained water. If a small hole develops at the base of a sac, little amphipods and worms may crawl in and use it for a refuge.

The visible sac may be a male or a ‘tetrasporophyte’ that developed on a microscopic female. The tetrasporophyte puts out spores in groups of four (hence the ‘tetra’), two males and two females. The females are mature sexually at a very young age. They catch non-motile sperm on special hairs, and the resulting zygotes develop into a new tetrasporophyte, while the tiny female disappears. The sources of sperm for the zygote are males of the previous generation, because the males produced at the same time as these females are not yet mature. A research study showed that the spores settle and germinate best on surfaces that are rough at a micro-scale, rather than on smooth surfaces.

Thanks to Dr. Sandra Lindstrom for a good field trip and Dr. Mandy Lindeberg for additional instruction.

Note: these algae, like many others, have had numerous common and scientific names over the years. Common names often vary from place to place. Changes in scientific names generally reflect altered and improved understanding of genetic relationships.

Early fall observations

swimming squirrels and a deadly flower

All around town, the maple trees are flaunting their famous reds and golds, at least on certain branches. In the forest, devil’s club leaves are turning yellow, setting off the clusters of red fruits and brightening the understory. Highbush cranberry shrubs sport variegated sprays of red and pink and yellow and everything in between, with the occasional bonus of bright red berries. High on the mountain slopes the deer cabbage offers another colorful palette, of orange and russet and gold. In the valleys, cottonwoods and willows are spangled with gold and yellow amidst the bronzy green—visual treats against the backdrop of somber green conifers.

The sockeye run in Steep Creek is finishing, so the bears are roaming around in search of alternate foods, while they wait for the coho to arrive. Bear scats show evidence of much consumption of northern ground cone, with some devil’s club seeds, currants, and highbush cranberries. The fish are few, but one day I watched a familiar female bear run down a sockeye, pin it to the bottom of the stream, and then pick up the flapping fish and tote it into the woods near the observation platform. There she ate the whole thing except the gills, starting with the eggs; one by one, she also lapped up all the eggs that got scattered around in the grass.

Someone once told me, in no uncertain terms, that red squirrels cannot swim—if you throw one into the water, it will just sink. Aside from the fact that most folks wouldn’t do that in the first place, the statement is simply not true (at least if the animal is unhurt). I once watched a red squirrel swimming between two islands in Glacier Bay. And recently I watched one deliberately cross a creek, jumping right in and paddling across. Its tail didn’t even get very wet and its back stayed dry. A very competent swimmer, across the current of the stream.

Photo by Bob Armstrong

On a walk up the ‘new’ road at Eaglecrest, we found a few late monkshood flowers. No bees seemed to be flying to pollinate them, but we were curious about how the flower ‘works.’ That is, how are the male and female parts arranged, and how would a bee transfer pollen? So we opened up a few flowers. Just inside the natural opening, where a bee would enter, is a tuft of stamens, which would place pollen on a bee as it crawled in. Mixed in among the stamens are the female parts, which would receive pollen. But if male and female parts are in the same place, does this plant pollinate itself or is there some way to avoid self-pollination?

A little bit of research revealed that monkshood species are generally protandrous (first male), meaning that the stamens shed mature pollen before the female part of the same flower is receptive. Bees commonly work from the bottom of the array of flowers, with older flowers, toward the top of the plant, where flowers are younger, so they encounter mature female-stage flowers before they reach the mature male-stage flowers. Before they leave the plant, they pick up pollen from the last-visited flowers. Then, when they fly to the next monkshood plant, they start again at the bottom, where they can deposit pollen from the first plant on receptive female parts of the next plant. In addition, monkshoods are largely self-incompatible: mostly unable to fertilize themselves.

Still to be determined, however, is why the entire flower is so complicated in structure.

Why have that ‘hood’ on top? Those purple petal-like pieces that make the flower are not really petals, they are sepals (parts that are structurally external to the petals; they are green in many other kinds of plants). In the back of the flower, under the hood, are two arching structures that are the true petals, and the nectary is located in a spur at the upper end. But why put the nectary way in back, when the working parts are up front? Bees are said to enter the flower, find the nectar, and then back out the way they came in, passing over the sexual parts as they do so. But the flower does not need to be so complex if that’s all the bees do. Next summer we should try to observe bees as they visit monkshood flowers, to see if we can solve these little mysteries.

By dissecting a few monkshood flowers, we found out that the nectar spurs are quite short, so short-tongued bees should be able to reach the nectar easily, without resorting to nectar theft (chewing through the hood and spur to get nectar without touching the sexual parts of the flower).

But flower handlers beware! Monkshood is very poisonous, and very little of it is needed to produce a nasty effect. Even touching it with your hands and then eating something with your hands, or smoking a cigarette, can apparently have undesirable consequences. Large doses are generally lethal.

One day we walked out toward Herbert Glacier but were thwarted in the last stretch by high water. Along the trail we noted a large white slime mold, artistically draped over a low stump. At several points on the side of the trail were stands of the prosaically named purple coral fungus. It grows in damp soils, sending up finger-like fruiting bodies of a distinctive purple color. It is not to be confused with the unrelated but catchily named deadman’s fingers, which is generally blackish (with a white core) and usually grows on decaying wood. I also found a small specimen of what I think was a white coral fungus. Elsewhere I’ve noted fist- to head-sized clumps of a highly branched yellow coral fungus.

Spatial overlap among bears…

…and between bears and humans

Coastal Alaska supports both black and brown bears, both of which inhabit the rainforest and potentially eat much the same kinds of food. Where they occur together, how do they get along?

In Southeast, both species occur in many areas, and one can watch both species fishing for salmon in places such as Anan Creek. Here the black bears tend to avoid the brown bears, but there are usually so many salmon that both kinds of bears feed well. But that is not always the case.

Brown bears achieve larger body size than black bears of the same age and gender. Larger body size allows brown bears to be dominant over black bears and potentially to exclude them from choice feeding areas. Salmon spawning runs are prime foraging places and brown bears are often capable of near- monopolies there. One study near Denali found that brown bears ate much more salmon than black bears, in general, and when salmon runs were poor, black bears got no salmon at all because brown bears prevented access to the streams. So in years of small salmon runs, black bears had poor body condition and poor reproduction.

Another study, on the Kenai Peninsula, also found that brown bears ate far more salmon than black bears. Occasional male black bears visited salmon runs but obtain few fish and no female black bears had access to the stream. Both species of bear ate berries extensively, but fruits made up a higher proportion of energy intake for black bears. Part of the Kenai Peninsula apparently lacks brown bears, for some reason, and in that area, black bears normally consume lots of salmon.

Although both species of bear occupy much of Southeast, there are broad areas where only one kind of bear has well-established populations. On Admiralty, Chichagof, and Baranof islands, only brown bears occur. But why, given that they co-occur with black bears in other areas? On the other hand, on the islands south of Frederick Sound, including Haida Gwaii, only black bears are found. However, fossil remains show that brown bears formerly occurred there , and brown bears are seen there upon occasion even now, but they do not establish breeding populations. Why are the browns absent in these regions? Selective hunting? Some subtle habitat change? An interesting puzzle.

Brown bear in Glacier Bay. Photo by Jos Bakker

Humans now occupy significant chunks of coastal Alaska, largely displacing bears from most urban and agricultural areas. Rather than deal here with the obvious issue of habitat usurpation by humans, I’d like to focus on the possible effects of hunting and bear-viewing activities. Human hunting pressure might change interactions among bears, if it is focused on one gender or if it significantly reduces bear density. In addition, we have so many bears that bear-watching has become a profitable business as well as a popular activity for local folks.

A study in south-central Alaska found that where brown bears are not hunted, males clearly dominate at most fishing sites except when fishing is poor; at good fishing sites, males were far more common than females. Big bears need to spend more time fishing to get enough fish to eat; fishing is very inefficient for them when capture rates are low. However, where bears are hunted, male brown bears were not more common than females at good fishing places. Hunting pressure is heavier on males than on females, reportedly, which would reduce their numbers. In addition, where they are pursued, males may become more wary than females, such that they sacrifice good fishing for perceived safety. Whatever the reason, fewer males meant that females, especially those with cubs, had more access to fishing sites.

Add bear-viewing humans into the mix of interactions, and researchers found that adult male brown bears tended to avoid the humans, showing more avoidance in areas where hunting pressure was higher. Males also avoided humans more when there were alternative foraging sites in the same region, but if there were no alternative sites, male tolerance of human viewers increased—and presumably females then got fewer fish.

A study in British Columbia found that females with cubs spend less time fishing when big males were active; these females had about a third less consumption of salmon than undisturbed females. Bear-viewing activity tended to displace the big males, providing mother bears with increased access to fish. Mere presence of humans had little effect on foraging of females.

Near the Mendenhall Visitor Center, most of the black bears that use the area are females and young bears; there are few adult males. Observers believe that here, too, bear-viewing humans provide smaller bears with a safe area to forage, where they are not displaced by big males. It would be interesting to learn where the adult male black bears in this region go to forage! At Pack Creek on Admiralty Island, most of the brown bears foraging on salmon in the estuary near the viewing area are females and subadults, and that the males tend to forage farther upstream, away from most humans. On Admiralty, hunting is generally harder on brown bear males than females, especially in spring, so perhaps males are rightfully more wary.

Black bear at Mendenhall Glacier. Photo by Bob Armstrong

Thus, the general consensus seems to be that females avoid big males when they can and take advantage of their absence when possible, including finding temporary refuge near bear-viewing activities on humans.

Wonderful Winterland

herons, swans, and an eagle’s dinner

I love just prowling around in the snowy woods, looking for whatever presents itself. Solo or shared, there is usually something of interest. Here are a few examples from the past two months.

In November, just after the first good freeze-up, I poked around on the Old River Channel (think Mendenhall River, maybe a hundred years ago or so).A great blue heron had paced–in vain—along the now-icy runnel below a beaver dam, where no fish could now be grabbed. Then I saw some huge prints of webbed feet, bigger than my hand. No goose or duck or gull; this could only have been a swan. Following the tracks, I came to a place on the ice where the swan, perhaps with some friends, had dithered around for a while. They too were cut off by the ice from any tasty green vegetation in the water below. As they dithered about, they left samples of previous meals on the surface of the ice.

By now, my path had been crossed by another retired biologist and well-behaved canine companion. Together we inspected the digested remains of swan dinners and concluded that the swans had nibbled on their own excreta, recycling the material and probably extracting more nutrients. Well, if you can’t reach the fresh stuff, perhaps this is a reasonable alternative! I wonder how often they do this—is it only occasional, for instance when ice blocks the access to fresh greenery?

Some of those huge webbed footprints led away from the resting and feeding site. They gradually got farther and farther apart, until the last strides were separated by at least seven feet. The very last one was matched with the brush of a single wingtip in the light snow. A seven-foot stride on shortish legs meant that bird was really hurtling itself into flight.

Although swans sometimes overwinter in Southeast, most of them migrate to slightly more southerly realms. Several swans had been seen in the upper Mendenhall River on the days before my little exploration, but increasing ice cover was making further stay a hungry proposition for them.

In midDecember, Out the Road (in Juneau that is a place, not just a direction), we noticed two eagles hunkered down on the bank of a small stream. They were intently staring at a dark, furry object in the water. We were ‘dying’ of curiosity, of course, but didn’t want to disturb the eagles. So we went on, saying we’d stop to look on the way back. When we did so, the eagles and the dark object were gone. All we could do, then, was check out the spot for any signs of what had been there. We found a beaver tail, some gobbets of flesh, and a rib. Perhaps the carcass had shifted farther under the ice at the edge of the stream, but maybe more likely, one of the eagles had appropriated the thing for itself. By midDecember, beavers are usually hanging out in their lodges, awaiting ice-out. So why this one was here, and how long it had been there, was puzzling.

Mid December also found us wandering around some of the ponds in the Mendenhall Glacier Recreation Area. Walking over the ice on the ponds gives one an entirely different perspective from one on the trails or in the thickets. A bonus is walking in actual sunshine! One pond has several beaver lodges that, in four years of monitoring, have never shown any sign of current occupancy by beavers. This time, we noticed small holes in the side of two lodges, with small footprints making a trail right into that doorway. It looked as if mink had moved in. Out in the middle of the pond there were three round holes in the ice, kept open, perhaps, by mink diving in for fish.

Just before Christmas, I ambled over another pond. By now, we had had several more nights of single-digit temperatures, and the ice was really solid. But there were two holes in the ice that had just recently frozen over. And there was a trackway, made by several animals, running from one hole to the other, and then on toward shore. Following these round-pawed tracks, I came upon a sizable hole under some tree roots, and there the tracks ended. I surmised that a family of otters had used this hole as a part-time den; in the past week or so, a group of three pups and an adult (presumably Mom) had been seen fishing in the few ice-free spots that remained.